(1) Field of the Invention
The present invention relates to a drying system for heating and drying paint applied to automobile bodies in an automobile body painting process. More particularly, the invention relates to a drying system for drying automobile bodies comprising a drying chamber including a device for transporting automobile bodies having closed bottoms, and a device for supplying hot air for heating and drying paint applied to the automobile bodies in the drying chamber.
(2) Description of the Prior Art
FIG. 5 of the accompanying drawings illustrates a known drying system of the type noted above. As seen, a hot air supplying device 3 includes outlet openings 3a for delivering hot air sent through feed ducts 3A into lower regions of a drying chamber 1, and suction openings 3b for withdrawing the hot air from upper regions of the drying chamber 1. In this system, therefore, the hot air supplied contacts outside surfaces of an automobile body while flowing upwardly through the drying chamber 1. More particularly, the known drying system is constructed to directly heat and dry paint applied to the outside surfaces of the automobile body by causing the hot air to contact the paint while paint applied to inside surfaces of the automobile body is heated and dried by heat conducted from the outside surfaces through the automobile body and by hot air entering by way of openings such as windows into contact with the inside surfaces. Number 2 in FIG. 5 indicates a carriage for supporting the automobile body. In order to recirculate the hot air for repeated use, the illustrated hot air supplying device 3 further includes a duct 3B for guiding the hot air withdrawn through the suction openings 3b to a fan 3C and a burner or other type of heater 3D.
In the case of an automobile body of Monocoque construction, however, a cabin and trunkroom have their bottoms closed by a floor panel of the automobile body. Such a closed construction includes only small bores or the like in certain parts thereof. Therefore, the floor panel impedes good drying of the paint where, as in the prior art, hot air is delivered only to lower regions of the drying chamber. In other words, interior portions of the automobile body under which the floor panel extends have little chance of exposure to the hot air entering from below. Such portions rely solely on the thermal conduction through the automobile body for heating since their contact with the hot air cannot be much expected. Furthermore, these interior portions, after the automobile body has been carried into the drying chamber, retain cool air similar in temperature to air outside the drying chamber. This cool air tends to stagnate in the interior portions, causing so much delay for these portions to reach a chamber temperature. Consequently, the inside surfaces below the windows, such as inside surfaces of the floor panel and lower side panels, tend to be insufficiently heated compared with their outside surfaces. If heat drying of the outside surfaces is used as reference for removal of the automobile body from the drying chamber, the above-noted interior portions closed by the floor panel below will emerge half dry, namely short of tempering. Conversely, if heat is applied until those interior portions become dry to a satisfactory degree, then the outside surfaces and other portions in direct contact with the hot air will become overheated which is unacceptable. This tendency is conspicuous where the automobile body has an increased strength for reinforcement and is difficult to heat by thermal conduction.
Thus, the conventional hot air drying system has encountered great difficulties in drying both outside and inside surfaces of automobile bodies in an optimal manner.